if a person or an organization is rotten to the core, it behaves in a way that is not honest or moral.

The whole legal system is rotten to the core.

• only time will tell
• only too
• on mind
• on no account must do
• on no account must do something
• on no account must someone do
• on no account must someone do something
• on no account should do
• on no account should do something
• on no account should someone do
• on no account should someone do something
• on occasion
• on order
• on own
• on own account
• on own head be it
• on own hook
• on own time
• on pain of
• on pain of death
• on pain of something
• on paper
• on person
• on pins and needles
• on principle